Initialize TypeORM for Group entity

Signed-off-by: David Mehren <git@herrmehren.de>

src/groups/groups.module.ts

@@ -1,4 +1,8 @@
 import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { Group } from './group.entity';
 
-@Module({})
+@Module({
+  imports: [TypeOrmModule.forFeature([Group])],
+})
 export class GroupsModule {}